The mouse has emerged as the premier animal model for investigations into human disease. The Jackson Laboratory (TJL) plays a central role in the development of mouse models for human diseases through the independent research programs of its scientific staff members. These projects require the capacity to detect and analyze often subtle phenotypes, which depends on the ability of the animal facility to house the mice under conditions that ensure optimum health and performance. TJL's Research Animal Facility (RAF) and associated animal health programs provide modern, state-of-the-art animal husbandry and veterinary care for the over 2,000 genetically defined mouse strains maintained at TJL. An effort is ongoing to upgrade all of the RAF to a barrier facility in which all mice are at equivalent, high health status. This undertaking facilitates exchange of mice with internal and external collaborators and ensures that all TJL investigators have access to the Laboratory's expanding phenotyping facilities, which will be housed in high-level barrier facilities adjacent to the RAF. The objective of the proposed project is to upgrade existing non-barrier animal rooms in the RAF to provide barrier animal rooms for TJL neuroscience investigators in a location with direct access to the shared phenotyping facilities. Funds are requested to 1) renovate and upgrade the four existing animal rooms on Level 3 of the RAF's Animal Research Laboratory (ARL) to create five barrier-level animal rooms, each containing a large procedure room; 2) upgrade the air-handling, environmental control, and monitoring systems for Level 3 of the ARL; 3) construct a personnel entry/exit locker on ARL Level 3; and 4) purchase portable, HEPA-filtered positively individually ventilated caging systems and mobile, HEPA-filtered ventilated changing stations for the new animal rooms.